This "thing" continues to hang on the trunk of my Cottonwood tree -- though it appears to be drying out and turning grayish. I would really love to know what it is and I'm hoping the experts at the Extension can help me! Thanks.

Hi Nicole,

Sorry for the delay in response.

From what I can see in the photo, you have a fungal fruiting body growing out of the tree trunk.  Based on the leaves, this is a willow tree rather than a cottonwood.  Many hardwood trees, including both cottonwoods and willows, are susceptible to decay fungi in dead wood.  Likely a wind-blown spore established in the wound on the tree; under the right weather conditions a fruiting body like this will be produced.

Trees weakened by decay fungi are prone to windthrow or breakage.  If the tree could cause personal injury or property damage were it to fail, you may wish to consult an arborist to determine the extent of the damage and if the tree should be removed.  In the majority of decay-fungi infections, the disease is not treatable.  Promoting tree health and avoiding tree-wounding are the best practices for preventing infections.

I hope this is helpful!

Cordially,

John